BACKGROUND
Syntaxins, a family of proteins involved in the docking of synaptic vesicles with the plasma membrane, display broad tissue distribution and contain carboxy-terminal hydrophobic domains that direct themselves to their respective intracellular compartments. Syntaxin 3 localizes to the apical plasma membrane and is involved in membrane fusion of apical trafficking pathways. Syntaxin 4 is crucial for normal insulin-stimulated glucose uptake in skeletal muscle and decreases in Syntaxin 4 protein levels result in reduction of whole-body insulin-stimulated glucose metabolism. Syntaxin 5 associates with p97 to regulate the assembly of transitional ER. Dephosphorylation of p97 stabilizes the p97/syntaxin 5 complex. Syntaxin 5 also exists in a SNARE complex containing Golgi Snare (GS) 28, GS15 and Ykt6. Syntaxin 6 facilitates homotypic fusion of immature secretory granules during maturation. Syntaxin 6 is widely expressed with higher expression levels in brain, lung and kidney. A proposed SNARE complex between Syntaxin 7 and VAMP7 or VAMP8 may regulate the fusion events that eventually lead to melanogenesis.